Scroll-type fluid transferring machine with deformable thrust bearing

ABSTRACT

A scroll-type fluid transferring machine of an improved construction, in which the bottom surface of the base plate of the orbiting scroll member and the bearing surface of the thrust bearing are well adapted even under a thrusting force during compression of the operating fluid, such scroll-type fluid transferring machine having its feature such that the surface of the thrust bearing to support the base plate of the orbiting scroll member, or the surface of the base plate of the scroll member supported by the thrust bearing is slanted in the radial direction so as to form the surface thereof in a center-concaved shape, wherein the inner peripheral side is concaved with respect to the outer peripheral side at a very small distance in the axial direction, or that an axial projection which is concentric with the thrust bearing and has a narrow width in the radial direction is provided between the opposed surfaces of the thrust bearing and the bearing frame in the vicinity of the center part in the radial direction between the inner peripheral side and the outer peripheral side of the thrust bearing, and further space gaps are provided between the mutually opposed surfaces at the inner peripheral side and the outer peripheral side of the projection.

This is a division of application Ser. No. 935,295, filed Nov. 26, 1986,U.S. Pat. No. 4,761,122.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

This invention relates to a scroll-type fluid transferring machine to beused as a compressor such as a refrigerant compressor, an aircompressor, and so forth; a fluid pump; a turbine expanding machine; andothers.

2. Discussion of the Background:

In the following, explanations will be given as to the conventionalscroll-type fluid transferring machine by taking a compressor as anexample.

First of all, the principle of the scroll compressor will be explainedbriefly.

FIGS. 1(a) to 1(d) of the accompanying drawing illustrate thefundamental structural elements of the scroll compressor and the theoryof its compression. In the drawing, a reference numeral 1 designates astationary scroll member, a reference numeral 2 indicates an orbitingscroll member, a numeral 3 refers to an outlet port, and a numeral 4refers to a compression chamber. A reference letter O designates a fixedpoint on the stationary scroll member 1, while a reference letter 0'denotes a fixed point on the orbiting scroll member 2. Both stationaryscroll member 1 and orbiting scroll member 2 are respectively in theform of a wrap 1a and a wrap 2a, each being constructed with an involutecurve, an arc, and so forth of the same shape, but being in a mutuallyopposite winding direction.

In the following discussion, the operation of this type of the scrollcompressor will be explained. The stationary scroll member 1 is in thestationary state with respect to the open space, while the orbitingscroll member 2 is combined with the stationary scroll member 1 andchanges its position at the respective moving angles of 0°, 90°, 180°and 270°, as shown in FIGS. 1(a), 1(b), 1(c) and 1(d) respectively,without changing its posture with respect to the open space. With themovement of the orbiting scroll member 2, the compression chamber 4 inthe form of a crescent defined between the wrap 1a of the stationaryscroll member 1 and the wrap 2a of the orbiting scroll member 2sequentially reduces its volume, whereby a gas confined in thiscompression chamber 4 is compressed and discharged from the outlet port3. During this compression stroke, a distance between the fixed pointsO--O' in FIGS. 1(a) to 1(d) is maintained constant, and, if a spaceinterval between the wraps is taken as a and the thickness of each ofthem is denoted as t, the distance (O--O') is represented asO--O'=a/2-t. Additionally, the space interval a corresponds to a pitchof the wrap.

The explanations given above are the outlines of the apparatus known asa scroll compressor.

In the following discussion, explanations will be given as to a concreteconstruction and operations of the conventional scroll compressor.

FIG. 2 is a side elevational view in longitudinal cross-section showinga compressing mechanical part of a conventional scroll compressor. InFIG. 2, a reference numeral 1 designates a stationary scroll memberconstructed with a wrap 1a such as in an involute form; a base plate (orceiling plate) 1b, from one surface side of which the wrap 1a isprojected downward; an outlet port 3 formed in one part of this baseplate 1b; and an inlet port 5 formed in another part thereof. A numeral2 refers to an orbiting scroll member constructed with a wrap 2a in thesame shape as that of the wrap 1a of the stationary scroll member 1, butwound in an opposite direction to that of the wrap 1a; a base plate (orbottom plate) 2b, from one surface side of which the wrap 2a isprojected outward; and a boss 13 projected downward from the othersurface of the base plate 2b. A reference numeral 4 represents acompression chamber defined by the wrap 1a of the stationary scrollmember 1, the base plate 1b, the wrap 2a of the orbiting scroll member2, and the base plate 2b. A numeral 6 refers to a bearing frame, anumeral 7 refers to a thrust bearing provided on the bearing frame 6 tohold the bottom surface of the base plate 2b of the orbiting scrollmember 2, and a numeral 8 refers to a main shaft having an eccentricbore 14, into which the boss 13 of the orbiting scroll member 2 isfitted in a freely rotatable manner. A reference numeral 9 denotes arotation-preventing mechanism constructed with an Oldham's coupling, andso forth, which functions to prevent the orbiting scroll member 2 fromits rotation around the boss 13 as its shaft and to cause it to revolvearound the main shaft 8 as its crank shaft. A numeral 10 refers to abalancer. These are the principal components for the compressionmechanical part of the scroll compressor. In this mechanical structure,the wrap 2a of the orbiting scroll member 2 and the wrap 1a of thestationary scroll member 1 are fitted together in a mutually oppositerelationship, and the boss 13 of the orbiting scroll member 2 is fittedinto the eccentric bore 14 of the main shaft 8. The main shaft 8 issupportively fitted in the bearing frame 6 in a freely rotatable manner,both bearing frame 6 and the stationary scroll member 1 being coupledtogether with screw-threaded bolts, etc. (not shown in the drawing).Furhter, the upper surface of the thrust bearing 7 mounted on thebearing frame 6 and the bottom surface of the base plate 2b of theorbiting scroll member 2 opposite to the wrap 2a come into contact eachother. The balancer 10 is fixed on one part of the main shaft 8 bypressing-fitting.

FIG. 3(a) through 6(b) are schematic diagrams for explaining thefunction of various thrust bearing sliding parts of conventional scrollcompressors, wherein FIGS. 3(a), 4(a), 5(a) and 6(a) respectivelyillustrate a state, in which a gas pressure is not present in thecompressor before or after its operation, while FIGS. 3(b), 4(b), 5(b)and 6(b) respectively show a state, in which the base plate 2a of theorbiting scroll member 2 is deformed by a thrust load imparted to itduring operation of the compressor. It should be noted that, throughoutFIGS. 3(a) to 6(b), reference letters δ₁ to δ₃ denote a quantity ofdisplacement of the base plate 2b of the orbiting scroll member 2 or adifference in height in the axial direction between the inner peripheralside and the outer peripheral side of hte thrust bearing 7.

FIGS. 3(a) and 3(b) illustrate a case, wherein the bottom surface of thebase plate 2b of the orbiting scroll member 2 constituting the slidingsurface with the upper surface of the thrust bearing 7 (in other words,the upper surface of the thrust bearing 7 constituting the slidingsurface with the bottom surface of the above-mentioned base plate 2b) isperpendicular to the direction of the axis, in the form of theirconstituent parts; that is to say, the inner peripheral side and theouter peripheral side of the thrust bearing constituting the slidingsurface are in the horizontal plane.

FIGS. 4(a) and 4(b) illustrate a case, wherein the inner peripheral sideof the upper surface of the thrust bearing 7 is in the form of acenter-convex by an amount δ₂ with respect to the outer peripheral sidethereof.

FIGS. 5(a) and 5(b) illustrate a case, wherein the bottom surface of thebase plate 2b of the orbiting scroll member 2 is in a center-convexedshape at the inner peripheral side of the thrust bearing 7 by an amountδ₃ with respect to the outer peripheral side thereof as shown in moredetail in FIG. 7.

FIGS. 6(a) and 6(b) show a state, in which the upper surface of thethrust bearing 7 is in a center-convexed shape by an amount δ₂ as is thecase with FIGS. 4(a) and 4(b), and, at the same time, the bottom surfaceof the base plate 2b of the orbiting scroll member 2 is in thecenter-convexed shape by an amount δ₃ as is the case with FIGS. 5(a) and5(b).

Incidentally, it should be noted that each of FIGS. 3(a) through 7 isexaggerated in its illustration of the thrust bearing 7 and the baseplate 2b of the orbiting scroll member 2 in their axial direction forbetter understanding of the explanations.

In the following discussion, an explanation will be made as to theoperations of the scroll compressor which is constructed in theabove-described manner. When a rotational torque is transmitted from thedrive part such as an electric motor, and so forth (not shown in thedrawing) to the main shaft 8 to start its rotation, the orbiting scrollmember 2 commences its turning. In this case, however, since theorbiting scroll member 2 is prevented from its rotation by therotation-preventing mechanism 9 provided on it, both stationary scrollmember 1 and orbiting scroll member 2 function to compress the operatingfluid on the basis of the principle of compression as described in theforegoing in reference to FIG. 1. In this instance, the orbiting scrollmember 2 perform its eccentric revolution, the static and dynamicbalancing of which is done by the balancer 10. Further, in such scrollcompressor, there occurs a thrusting force which tends to separate thestationary scroll member 1 and the orbiting scroll member 2 in the axialdirection during compression of the operating fluid. This thrustingforce is undertaken by holding the bottom surface of the base plate 2bof the orbiting scroll member 2 on the upper surface of the thrustbearing 7 provided on the bearing frame 6.

The conventional scroll compressor as constructed in the above-describedmanner increases the fluid pressure towards the center of bothstationary and orbiting scroll members during its operation as will beunderstandable from the operating principle of the scroll compressorshown in FIG. 1, whereby the base plate 2b of the orbiting scroll member2 is deformed ithe center-convexed shape by an amount δ₁, for example,owing to a load exerted by the compressed gas, as shown in FIG. 3(b). Onaccount of this, the bottom surface of the base plate 2b of the orbitingscroll member 2 and the inner peripheral edge of the upper surface ofthe thrust bearing 7 bring about concentrated sliding contact. By thisphenomenon taking place during the operation of the compressor, thissliding part becomes apt to readily bring about abnormal wear or seizurewith the consequent various problems to occur such that the compressoris damaged, mechanical loss of the compressor increases, and so on. Suchsliding phenomenon appears consequently when the upper surface of thethrust bearing or the base plate 2b of the orbiting scroll member 2 isin the center-convexed shape at its inner peripheral side with respectto the outer peripheral side thereof owing to its state at the time ofmachining, etc. as shown in FIGS. 4(a), 4(b), 5(a) and 5(b), or whenboth upper surface of the thrust bearing 7 and bottom surface of thebase plate 2b are in the center-convexed shape at their inner peripheralside with respect to the outer peripheral side, all these having beenliable to bring about abnormal friction, seizure and other undesirablephenomena in the thrust bearing.

SUMMARY OF THE INVENTION

The present invention aims at solving the problems mentioned above, and,more particularly, seeks to provide a scroll-type fluid transferringmachine such as scroll compressor, etc. which has high operationalreliability at its bearing part, and in which the bottom surface of thebase plate of the orbiting scroll member and the bearing surface of thethrust bearing are well adapted, even under a thrusting force impartedthereto during operation of the scroll-type fluid transferring machine,i.e., during compression of the operating fluid.

That is to say, the scroll-type fluid transferring machine according tothe present invention, in one aspect of it, is constructed with astationary scroll member and an orbiting scroll member, each being inthe shape of wrap formed by an involute curve, etc. and beingprojectively attached onto a base plate to define a compression chamberby combining them in a manner to mutually offset said helices; a mainshaft for transmitting drive force from a prime mover such as anelectric motor to said orbiting scroll member; a bearing frame whichholds said orbiting scroll member and said main shaft to share to thrustload to be imparted to each of them; a thrust bearing provided on saidbearing frame and functioning to hold said base plate of said orbitingscroll member and a rotation-preventing mechanism to prevent saidorbiting scroll member from its rotation around the axis and to causethe same to revolve around said main shaft, wherein the surface of saidthrust bearing holding the base plate of said orbiting scroll member, orthe surface of said base plate of said orbiting scroll member held bysaid thrust bearing is slanted in the radial direction so as to form thesurface thereof in a center-concaved shape, wherein the inner peripheralside is concaved with respect to the outer peripheral side at a verysmall distance in the axial direction.

Moreover, the scroll-type fluid transferring machine according to thepresent invention, in another aspect of it, is constructed with astationary scroll member and an orbiting scroll member, each of which isin the form of a wrap such as an involute curve, etc. and which isprojectively attached onto a base plate to define a compression chamberby combining them in a manner to mutually offset said wraps; a mainshaft for transmitting drive force from a prime mover such as anelectric motor to said orbiting scroll member; a bearing frame whichholds said orbiting scroll member and said main shaft to share a thrustload to be imparted to each of them; a thrust bearing provided on saidbearing frame and functioning to hold said base plate of said orbitingscroll member; and a rotation-preventing mechanism to prevent saidorbiting scroll member from its rotation around its axis and to causethe same to revolve around said main shaft, wherein at least one axialprojection concentric with said thrust bearing and having a narrow widthin the radial direction is provided between the opposed surfaces of saidthrust bearing and said bearing frame in the vicinity of the center partin the radial direction between the inner peripheral side and the outerperipheral side of said thrust bearing, and a space gap is provided atthe inner peripheral side and the outer peripheral side of theprojection between said mutually opposed surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

Various ways of carrying out the invention are described in detailhereinbelow with reference to the accompanying drawings which illustratea few preferred embodiments, in which:

FIGS. 1(a), 1(b), 1(c) and 1(d) are respectively schematic illustrationsshowing the operating principle of the scroll compressor, in which it isin different operating conditions;

FIG. 2 is a side elevational view in longitudinal cross-section showingthe compression mechanical part of the conventional scroll compressor;

FIG. 3(a), 4(a), 5(a) and 6(a) are respectively schematic illustrationsfor explaining the functions of different thrust bearings of theconventional scroll compressor in their non-operating state;

FIG. 3(b), 4(b), 5(b) and 6(b) are respectively schematic illustrationsfor explaining the functions of different thrust bearing of theconventional scroll compressor in their operating state;

FIG. 7 is a side elevational view in longitudinal cross-section showingthe orbiting scroll member used in the embodiment of FIGS. 6(a) and6(b);

FIG. 8 is a side elevational view in longitudinal cross-section showingthe compression mechanical part of the scroll compressor according toone embodiment of the present invention;

FIG. 9(a), 9(b) and 9(c) are schematic illustrations for explaining thefunctions of the same scroll compressor of FIG. 8 in its differentstates;

FIG. 10(a) and 10(b) are respectively a plan view and a longitudinalcross-sectional view of the thrust bearing for the same scrollcompressor as shown in FIG. 8;

FIG. 11 is a side elevational view in longitudinal cross-section showingthe orbiting scroll member for the scroll compressor in accordance withanother embodiment of the present invention;

FIG. 12 is a side elevational view in longitudinal cross-section showingthe compression mechanical part of the scroll compressor in accordancewith still another embodiment of the present invention;

FIG. 13 is a plan view of the thrust bearing for the same scrollcompressor as shown in FIG. 12;

FIG. 14(a) and 14(b) are schematic fragmentary views in longitudinalcross-section for explaining the function of the thrust bearing in FIG.13 in its different state; and

FIG. 15 is a side elevational view in longitudinal cross-section showingthe main part of the scroll compressor in accordance with otherembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, the present invention will be described inreference to FIGS. 8 through 10(b) showing one embodiment of the presentinvention.

Referring to FIG. 8, in which the same reference numerals as those inFIG. 2 designate the same or corresponding parts, a numeral 16a refersto the upper surface of a thrust bearing 16 separately formed from thebearing frame 6. This upper surface 16a is slanted in the radialdirection; that is to say, it is machined to have a center-concavedshape, wherein its inner peripheral side is concaved for a very smalldistance of from 10 to 20 μm downward in the axial direction withrespect to its outer peripheral side. A numeral 16b refers to a spacegap between the upper surface 16a of the thrust bearing 16 and the lowersurface of the base plate 2b of the orbiting scroll member 2, the spacegap being formed at the time of assembly of these parts. A numeral 17refers to a screw-threaded bolt for fixing the thrust bearing 16 ontothe upper surface of the bearing frame 6. In order that the head 17a ofthis screw-threaded bolt 17 may not project from the upper surface 16aof the thrust bearing 16, a recessed part 16c to receive the head 17a ofthe screw-thereaded bolt 17 therein is formed in one part of this uppersurface 16a.

FIGS. 10(a) and 10(b) are respectively a plan view and a longitudinalcross-sectional view of the thrust bearing. In FIG. 10(a), a referencenumeral 15 refers to grooves for lubricating oil which are radiallyformed on the upper surface of the thrust bearing 16.

FIGS. 9(a), 9(b) and 9(c) are schematic illustrations for explaining thefunction of the sliding part of the thrust bearing in this firstembodiment of the present invention, in which FIG. 9(a) shows a statewherein no gas pressure is existent in the scroll compressor, and FIGS.9(b) and 9(c) show respectively the states wherein the base plate 2b ofthe orbiting scroll member 2 is deformed at the time of the thrust loadbeing imparted to it. It should be noted that the construction of thescroll compressor in this first embodiment other than those as describedabove is similar to that of the conventional scroll compressor shown inFIG. 2.

In this embodiment of the scroll compressor of the construction asdescribed above, the thrust bearing 16 is formed in the center-concavedshape as shown in FIG. 9(a) so that, when the base plate 2b of theorbiting scroll member 2 is deformed by the thrust load to be generatedat the time of compression of the gas during the operation of thecompressor, the bottom surface of the base plate 2b may be deformed inthe center-convexed shape. With this construction, the inner peripheraledge of the upper surface 16a of the thrust bearing 16 becomes able tosupport the bottom surface of the base plate 2b in the state of itsbeing deformed by the gas pressure, and wiht a large bearing area, butwithout its coming into the concentrated contact with the bottom surfaceof the base plate 2b of the orbiting scroll member 2 as shown in FIG.9(b). At this instant, there may be a possibility of the contact of theouter peripheral side taking place at the sliding surface between thebottom surface of the base plate 2b of the orbiting scroll member 2 andthe upper surface 16a of the thrust bearing 16, depending on the gaspressure, as shown in FIG. 9(c). However, since the bearing area isproportionate to the square of the radius, if a ratio of the innerdiameter to the outer diameter of the thrust bearing 16 is assumed to be1:2, the effective bearing area of the upper surface 16a of the thrustbearing 16 becomes four times as large as the conventional sliding atthe inner peripheral edge, whereby its capacity for the bearing load canbe remarkably improved. It should, however, be noted here that, when theheight δ₄ of the upper surface 16a of the thrust bearing 16 in thecenter-concaved shape assumes a value ten times or more, for example, aslarge as the absolute value δ₁ of the height of the base plate 2b of theorbiting scroll member 2 to be deformed by the thrust load, the uppersurface 16a of the thrust bearing 16 performs the sliding with theabove-mentioned base plate 2b at the outer peripheral side thereofduring operation of the compressor to thereby bring about abnormalfriction or seizure. Consequently, the upper limit of the height δ₄ ofthe center-concaved upper surface 16a is required to be kept three tofour times as high as the absolute height δ₁.

FIG. 11 is a side elevational view in longitudinal cross-section of theorbiting scroll member according to the second embodiment of the presentinvention. In this embodiment, the bottom surface 2c of the base plate2b of the orbiting scroll member 2 is made to assume a center-concavedshape with the inner peripheral side thereof being concave by about 10μm with respect to the outer peripheral side. (Incidentally, its shouldbe noted that the construction of the scroll compressor in thisembodiment other than those as described in the preceding is similar tothat as shown in FIG. 2.) In this second embodiment, too, there can beobtained the same resulting effect as that in the embodiment shown inFIGS. 8 to 10(b), wherein the above-mentioned bottom surface 2c preventsthe upper surface of the thrust bearing from performing contact with theinner peripheral edge.

Further, in the present invention, the thrust bearing may be integrallyformed with the bearing frame. Furthermore, the present invention may beapplied not only to the scroll compressor in the above-describedembodiment, but also to the fluid pumps, turbine compressors, and soforth.

As has been described in the foregoing, the scroll-type fluidtransferring machine according to the present invention is so formedthat the supporting surface of the thrust bearing for the orbitingscroll member or the surface of the orbiting scroll member to besupported by the thrust bearing is slanted in the radial direction toassume a center-concaved shape, such that consequently that there can bederived such effects that the one-side sliding contact of the uppersurface of the thrust bearing to the inner peripheral edge due todeformation of the base plate of the orbiting scroll member duringcompression of the fluid can be eliminated, whereby damage to themachine due to the abnormal wear and seizure at the sliding part, aswell as increase in the mechanical loss can be prevented.

FIGS. 12 to 14(c) illustrate the third embodiment of the presentinvention. In this embodiment, the thrust bearing and the base plate ofthe orbiting scroll member do not bring about the concentrated contactirrespective of the deformation of the base plate of the orbiting scrollmember due to the thrust load exerted by the compressed gas during theoperation of the compressor, or irrespective of whether the shape of thesliding surface of the base plate of the orbiting scroll member iscenter-convexed or center-concaved at its inner peripheral side withrespect to the outer peripheral side, thereby relaxing the machiningtolerance of the above-mentioned base plate.

FIG. 12 is a side elevational view in longitudinal cross-section showingthe compression mechanical part of this third embodiment. In thedrawing, the same reference numerals as those in FIG. 8 designate thecorresponding parts. In this embodiment, the thrust bearing 18 and thebearing frame 6 are separately constructed, and a projection 18cconcentric with them is projected in the axial direction from the bottomsurface of the thrust bearing 18, with which it is integrally formed.The projection 18c, as shown in FIG. 13, is disposed at the center partin the radial direction between the inner peripheral side and the outerperipheral side of the thrust bearing 18 with its width being madenarrow in its projecting direction with respect to its radius. Thethrust bearing 18 is fastened to the upper surface of the bearing frame6 with a screw-threaded bolt 17 passing through the projection 18c ofthe thrust bearing 18 in the axial direction. The lower end surface ofthe projection 18c is held on the upper surface of the bearing frame 6.Moreover, a recessed part 18d is formed in one part of the upper surfaceof the thrust bearing 18, in which a head 17a of the screw-threaded bolt17 is housed, and also, space gaps 18a and 18b are respectively formedbetween the opposed surfaces of the thrust bearing 18 and the bearingframe 6 at the inner peripheral side and the outer peripheral side ofthe projection 18c.

FIG. 13 is a plan view of the thrust bearing 18, on the upper surface ofwhich grooves 15 for lubricating oil are radially formed.

FIGS. 14(a) and 14(b) are fragmentary side elevational views inlongitudinal cross-section showing the function of the sliding partbetween the thrust bearing 18 and the base plate 2 of the orbitingscroll member 2 according to this embodiment. (It should be notedincidentally that the construction of this embodiment other than thosementioned in the preceding is similar to that in FIG. 2.)

In the scroll compressor according to this embodiment of the presentinvention in its construction as described above, the gas confined in itis compressed during its running; and, when the base plate 2b of theorbiting scroll member 2 is deformed by the thrusting force generatedfrom the compression, the thrust bearing 18 to be subjected to thisthrusting force is also deformed in the center-concaved shape so as tofollow the deformation in the base plate 2b of the orbiting scrollmember 2 with the consequence that no concentrated contact takes placeat the sliding part between the bottom surface of the base plate 2b andthe top surface of the thrust bearing 18. Further, when machining theorbiting scroll member 2, if the bottom surface of the base plate 2b ofthe orbiting scroll member 2 is formed in the center-concaved shape atits inner peripheral side with respect to its outer peripheral side asshown in FIG. 11, the thrust bearing 7 is deformed so as to conform tothe shape of the sliding surface thereof, even before the bottom surfaceof the base plate 2b has not yet been deformed by the compressed gas,with the result that no one-sided contact is brought about at the outerperipheral edge of the above-mentioned sliding surface.

FIG. 15 illustrates the scroll compressor according to the fourthembodiment of the present invention, in which a projection 7c concentricwith the thrust bearing 20 is projectively provided on the bearing frame6, but not on the thrust bearing per se, the rest of the constructionbeing the same as that shown in FIG. 12.

With this embodimental construction, too, the same resulting effect asthat obtained with the embodiment of FIG. 12 can be realized.

In the present invention, the thrust bearing may be coupled with one ofany appropriate connecting means such as pin, fitting, etc. other thanthe screw-threaded bolt for the bearing frame, or it may be formedintegrally with the bearing frame. Further, the present invention mayalso be applied to various scroll-type fluid transferring machine suchas fluid pumps, turbine expanders, etc. other than the scrollcompressor.

As has been explained in the foregoing, the scroll-type fluidtransferring machine according to the present invention has the axialprojection, which is concentric with the thrust bearing and has a narrowwidth in the radial direction, provided between the opposed surfaces ofthe thrust bearing and the bearing frame in the vicinity of the centerpart in the radial direction between the inner peripheral side and theouter peripheral side of the thrust bearing, and further has space gapsprovided at the inner peripheral side and the outer peripheral side ofthe projection positioned between these opposed surfaces. With suchconstruction, therefore, when the base plate of the orbiting scrollmember is deformed by a load in the thrusting direction duringcompression of the fluid, the space gap between the inner peripheralside and the outer peripheral side of the projection of the thrustbearing and the bearing frame is slightly deformed, which in turn causesthe thrust bearing to deform to follow the deformation of the baseplate, with the consequence that, whatever the shape of the slidingsurface of the base plate of the orbiting scroll member might be, therecan be obtained various effects such that the thrust bearing and thesliding part of the above-mentioned base plate does not bring about theone-sided contact, that the damage to the machine and increase in themechanical loss due to abnormal wear, seizure etc. of the sliding partcan be prevented, and further that the machining tolerance on thesliding surface of the base plate of the orbiting scroll member can berelaxed.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

We claim:
 1. A scroll-type fluid transferring machine provided with astationary scroll member and an orbiting scroll member, each being inthe shape of a wrap formed by an involute curve or the like and beingprojectively attached onto a base plate to define a compression chamberby combining them in a manner to mutually offset said wrap; a main shaftfor transmitting drive force from a prime mover such as an electricmotor to said orbiting scroll member; a bearing frame to hold saidorbiting scroll member and said main shaft for sharing a thrust load tobe imparted to each of them; a thrust bearing mounted on said bearingframe for supporting said base plate of said orbiting scroll member; anda rotation-preventing mechanism to prevent said orbiting scroll memberfrom rotation around its axis and to cause it to revolve around saidmain shaft, said fluid transferring machine being characterized in thatan axial projection, which is integral with and concentric with saidthrust bearing and has a narrow width in the radial direction is fixedto said bearing frame and is provided between the opposed surfaces ofsaid thrust bearing and said bearing frame in the vicinity of the centerpart in the radial direction between the inner peripheral side and theouter peripheral side of said thrust bearing, said axial projectionbeing annular and extending in an axial direction from a bottom surfaceof said thrust bearing and that space gaps are provided between saidmutually opposed surfaces at the inner peripheral side and the outerperipheral side of the projection.